The invention relates to means for detecting particles suspended in a fluid medium. While the invention has particular application for use with hydraulic fluids it will be understood that it also has application to other fluids. The apparatus in accordance with the invention may be used advantageously with expensive hydraulically operated machinery. Applications include machinery used in the military, aerospace, machine tool, earth moving, and other commercial fields. Such machinery, in addition to being relatively expensive, often will have high requirements for reliability and minimizing wear of the associated hydraulic system and often represents a large capital investment. A malfunction of such machinery may seriously delay the performance of other parts of a project. For example, earth moving equipment may be required to function on schedule in order to complete a critical part of a project, so that other parts may be completed. In many other applications, the consequential effects of commercial, military or aerospace equipment failing may be very significant.
Various devices are known for such applications. Much of the equipment of this type is relatively delicate laboratory type equipment which is not wholly satisfactory for field applications. In addition, much of the prior art apparatus is expensive and accordingly has not been widely accepted commercially.
One reason for the relatively great expense of the earlier apparatus is that they have in many cases utilized a relatively expensive and complicated lens system.
Such apparatus is shown in U.S. Pat. No. 2,789,765, which includes apparatus which requires scanning by an electron beam to produce signals in a manner similar to that employed in some television cameras. Other structures are shown in U.S. Pat. Nos. 2,656,508; 2,379,158; 2,791,377; 2,791,697; and 2,791,150.
It is a primary object of the invention to provide apparatus which will indicate the presence of matter such as contamination in a fluid and which will function in typical military, aerospace and commercial environments.
It is another object of the invention to provide apparatus which will improve the reliability and reduce maintenance costs of the cooperating hydraulic equipment.
It is another object of the invention to provide apparatus which is portable.
Another object is to provide apparatus which may be used independently to permit checking of hydraulic reservoirs in different hydraulically operated equipment or may be assembled as an integral part of a piece of machinery or of mobile equipment.
Yet another object of the invention is to provide apparatus which is simple in design and thus easy and inexpensive to manufacture.